Fluid motor control means and method



July 2, 1968 r w. J. BIENKO 3,390,526

FLUID MOTOR CONTROL MEANS AND METHOD Filed Nov. 12, 1965 v v I 26 Process l Refrigerant Condenser V w l Refrigerant Com pressor Pei'rigerant Evaporator Turbine Exhaust INVENTOR. WALTER J. BIENKO BYW ATTORNEY.

United States Patent 3,390,526 FLUID MOTOR CONTROL MEANS AND METHOD Walter J. Bienko, Dover, Ohio, assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Nov. 12, 1965, Ser. No. 507,283 6 Claims. (Cl. 60-102) ABSTRACT OF THE DISCLOSURE A control system for a power plant employing a first turbine and a second turbine connected together with a refrigerant compressor to a common drive shaft wherein the load on the refrigeration compressor is regulated so as to assure satisfaction of a variable process requirement communicating with the exhaust of the first turbine.

This invention relates broadly to the control of fluid machinery. More particularly, this invention relates to a control system for two fluid powered turbines connected to a common drive wherein two variable loads, independent of one another present separate demands on the apparatus.

Equipment of the type to which the control system forming the subject of this invention pertains is employed to satisfy a refrigeration demand while providing turbine exhaust fluid to satisfy a concurrent process demand. Under the circumstances, a boiler supplies steam as a motive fluid to the two turbines, connected to a common drive shaft, in parallel. The first turbine exhausts to a conduit or a reservoir subject to a demand for the fluid as a constituent in a process employed in the manufacture of a product. The second turbine is employed to provide additional power, as needed, to drive a refrigerant compressor secured to the common drive shaft. The second turbine exhausts to a condenser communicating with the boiler through a pump as is conventional in the art.

This invention has for its principal object the provision of a control system for automatically operating valves regulating the supply of steam to the turbine in such a manner that the two variable demands are satisfied first 'by the operation of the first turbine and second by the operation of the first and second turbines should such be required.

Another object of the invention is the provision of a control system of the kind described wherein pressure and/or temperature responsive cont-r01 devices are employed in conjunction with a pneumatic control fluid to produce signals to the valves regulating the supply of steam to the turbines.

A further object of the invention is the provision of a method of controlling the operation of apparatus involving two fluid machines regulating a common drive shaft so as to satisfy two independent variable demands on the apparatus.

In attaining these objects, there is provided a control system for regulating the supply of motive fluid to first and second turbines secured to a common drive shaft comprising means for regulating the supply of motive fluid to the first turbine in response to a first variable demand thereby imparting rotary movement to the common drive shaft, means for regulating the supply of motive fluid to the second turbine in response to a second variable demand substantially independent of the first demand, and electrically operated means responsive to the speed of the drive shaft for adjusting the first means in the event the 3,390,526 Patented July 2, 1968 shaft speed developed in response to the operation of the first means exceeds that necessary to satisfy the second demand.

Other objects and features of the invention will be apparent upon a consideration of the ensuing specification and drawings in which:

FIGURE 1 is a schematic view of an apparatus to which the control system forming the subject of this invention may be applied; and

FIGURE 2 is a schematic view illustrating the control system with functional symbols, forming the subject of this invention.

Referring more particularly to FIGURE 1 for an illustration of a type of plant to which the invention applies, there is shown a boiler 10 for generating motive fluid, which in this embodiment is steam, for supply to turbines 12 and 14 mechanically connected to a drive shaft 16. Also secured to the drive shaft 16 is a refrigerant compress-or 18 forming part of a refrigeration machine for supplying chilled water to satisfy a variable cooling requirement. Turbine 12 receives steam through valve 22 and exhausts through conduit 24 to a reservoir, not shown, where it may be stored for use in a process for fabricating a product. In some instances, the steam flowing in exhaust conduit 24 may be employed directly in the process. It will be appreciated that the rate of product manufacture may vary and thus create a variable process demand for the steam flowing from turbine 12. Turbine 14 is served by steam admission valve 23. The exhaust of turbine 14 flows to a condenser 26 where it is liquefied and returned by a pump to the boiler to be transformed again to steam so as to provide a continuous cycle of fluid flow.

The control system for automatically operating the turbines 12, 14 is arranged so that, to the extent possible, the shaft speed, necessary to satisfy a particular load on the refrigeration machine, will be provided by the motive fluid (steam) expanded through turbine 12 exhausting to the process with provision for supplying steam to turbine 14 when the demand on the refrigeration machine requires a shaft speed in excess of the speed developed by turbine 12 and with the additional provision of reducing the supply of steam to turbine 12 When the refrigeration demand is reduced so that a shaft speed less than the speed developed by turbine 12 will obtain. Under the latter condition, steam is passed from the boiler through a valve directly to the exhaust of turbine 12 to satisfy the process demand.

The described pattern of operation is achieved by the use of a plurality of control elements operating in a predetermined manner. To this end, there is shown a pneumatic control system employing air under pressure from any convenient source, not shown. Certain elements such as temperature transmitters and pressure sensors act in conjunction with the pneumatic system to provide signals to controllers regulating the supply of steam to the turbines 12 and 14. In order to satisfy the process demand, the term applied to describe the varying requirement for the fluid exhausted from turbine 12, there is provided an adjustable pressure controller 34 wherein a signal from the controller, having communication with the source of control air, represents a particular process demand. The signal is transmitted via line 36 to a totalizer 38 where it is compared with a signal representing the actual pressure in the exhaust of turbine 12. This latter signal varies of course with a variation in process demand and is sensed by a pressure sensor 40 which transmits a force in opposition to the force applied to the totalizer via line 36. A predetermined unbalance causes a pneumatic signal to be transmitted via line 42 to a paralleling relay 44, the output of which provides a pressure signal in line 46 to the valve 22 controlling supply of steam to the turbine 12. Thus, the supply of steam to turbine 12 necessary to provide a predetermined pressure in the exhaust of turbine 12 is assured.

As pointed out above, the speed of shaft 16 responsive to the flow of steam through turbine 12 either exceeds, equals or is less than the speed required to satisfy a simultaneous demand on the refrigeration machine, the compressor of which is coupled to shaft 16. In other words, satisfaction of the refrigeration demand requires a pumping rate directly related to the impeller speed in the compressor. The refrigeration demand is reflected by the temperature of the product of the refrigeration machine, namely chilled water flowing from the machine to a point of use and returning to the machine to reject the heat absorbed at the point of use. In the apparatus disclosed, mechanism is provided for regulating the valve 23 supplying steam to turbine 14. Principally, the mechanism includes a hydraulic governor 48 that automatically adjusts the supply of steam to the turbine 14 in response to a control signal. The control signal is developed by a temperature sensor 50' responsive to the temperature of the chilled water. The sensor 50 may be a thermal responsive fill system feeding a pressure signal to a totalize-r 52 and to the governor 48 to adjust the latter in relation to the demand. In the totalizer 52, the force represented by the pressure signal is opposed by a force representative of the actual speed of the shaft 16 developed by the turbine 12 as it satisfies the concurrent process demand. In the event a predetermined unbalance occurs in totalizer 52, a resultant pneumatic signal is forwarded via line 54 to the t-otalizer 44 to adjust the resultant signal emanating from the paralleling relay 44 via line 46. With this arrangement, should the shaft speed as developed by the process demand exceed the speed necessary to provide a compressor pumping rate (refrigeration demand), the signal in line 46 will be reduced and the flow through turbine 12 will also be reduced. This may cause a drop in the exhaust pressure of turbine 12 below that necessary to satisfy the process demand. In that case, flow of steam will be through line 80 connecting the boiler directly with the exhaust conduit 24-.

Should the speed of shaft 16, as developed through satisfaction of the process demand, be below that required to satisfy the refrigeration demand, totalizer 52 will not send a signal to paralleling relay 44 and governor 48 will open valve 23 so that steam will 'be supplied turbine 14 from boiler 10 to increase the shaft speed to a level suflicient to satisfy the refrigeration demand. The signal in line 42 maybe forwarded to a totalizer 56 where it can be compared with the signal emanating from the chilled water sensor to provide a resultant signal for transmission via line 49 which is anticipatory in the direction of a particular change to minimize hunting.

In measuring the shaft speed to produce a pressure signal to compare with the force produced by the chilled water temperature sensor 50, it has been determined that the shaft speed should be measured by using a tachometer generator 61, readily available commercially as Weston Model 75 8-GF, secured to the shaft. Associated therewith is a transformer 63 also readily available commercially as Weston Model 9906. The transformer in turn provides an electric signal to a transducer 65 commercially available as Moore Products Model 77-3, which in turn regulates a pneumatic signal applied to relay 52.

With the control system described, there is preferably provided a manual-automatic station having communication with the source of control fluid so that the apparatus may be started. The type of control, while not shown, is conventional and is mentioned merely for the purpose of describing a complete system.

With the apparatus control system described, steam is caused to flow from the boiler 10 to the valves 22 and 23 for admission to the turbines 12 and 14. The control system is such that the process demand for steam will cause a signal to be produced that will govern the flow of steam to turbine 12. The extent that the ensuing shaft speed can satisfy a simultaneous demand for refrigeration is detected by the elements 50 and 61 acting in concert with the elements 44, 52 and 56. If too great a shaft speed is detected, the elements automatically operate to revise the signal transmitted to the valve 23 to decrease the shaft speed. If the shaft speed created by the process demand is insuflicient to satisfy the refrigeration demand, additional steam is forwarded to the turbine 14. The excess shaft speed ensuing does not seriously affect the exhaust from turbine 12, for, at the new rate of shaft speed dictated by the increased refrigeration requirement, the back pressure (exhaust pressure) on turbine 12 will vary the stage efliciency only of the turbine 12.

While I have described preferred embodiments of the present invention, it is understood that this invention may be otherwise embodied within the scope of the following claims.

I claim:

1. A control system for regulating the operation of first and second fluid driven turbines secured to a common drive shaft providing rotary movement to pumping means subject to a variable demand wherein the exhaust of the first of said turbines is utilized to satisfy a variable process demand, comprising:

first means for supplying motive fluid to said first turbine in response to the process demand thereby imparting rotary motion to the common drive shaft, second means for supplying motive fluid to said second turbine in response to a demand imposed on said pumping means, requiring a shaft speed in excess of that necessary to satisfy a concurrent process demand,

electro responsive means for adjusting said first means in the event the shaft speed developed by the first means exceeds that necessary to satisfy the variable demand imposed on said pumping means. 2. The control system set forth in claim 1 wherein said first means includes a pneumatic system providing a control fluid and pressure responsive control elements operatively associated with the pneumatic system to provide a signal reflecting the process demand.

3. The control system set forth in claim 1 wherein said second means includes a source of control fluid, temperature responsive control elements operatively associated with the source of control fluid to vary the pressure thereof in response to a predetermined change in the demand on said pumping means.

4. The control system set forth in claim 1 wherein said third means includes a source of control fluid ope-ratively associated with said electro responsive means to provide a signal indicating shaft speed.

5. The cont-r01 system set forth in claim 4 including means for receiving the shaft speed signal, comparing it to the demand on said pumping means and providing a resultant signal to modify the action of the first means. 6. The method of controlling the operation of first and second turbines secured to a common drive shaft wherein the exhaust of the first turbine is employed to satisfy a variable process demand, and the power developed by the drive shaft is employed to satisfy a variable pumping demand which consists in the steps of supplying motive fluid to drive said first turbine in response to said process demand while simultaneously providing rotary movement to said drive shaft,

measuring the shaft speed developed by the supply of motive fluid to the first turbine to determine if said shaft speed is sufiicient to satisfy the simultaneous pumping demand, and

selectively reducing the supply of motive fluid to the first turbine in the event the shaft speed is excessive and supplying motive fluid to the second turbine 5 when the shaft speed is less than that necessary to satisfy the load on the pumping means.

References Cited UNITED STATES PATENTS 1,154,210 9/1915 Santry 60-102 X 1,185,246 5/1916 Santry 60-102 6 Scheltens 60-102 X Kieser 60-102 X Kieser 60-102 Guilkauman 60-102 X 5 MARTIN P. SCHWADRON, Primary Examiner.

ROBERT R. BUNEVICH, Examiner. 

